Hello, @ravensong . . . I have a noisy house and three EMO. Yes, the sensitivity has changed. I also do not like having to yell at the little guys, but there is one thing I discovered and one thing I can suggest.
Make sure you are facing him when you call him distinctly and a little louder. Think of it like trying to get the attention of a child when they are distracted with something else.
Also, since he is new to you, he may need to be able to recognize your vocal characteristics. You can submit your voice to this training page so that your voice can be added to his recognition software which should help a lot.
My best to you and let us know if these things help.